Their names may sound innocuous. But for environmentalists, they’re bad actors — invasive species that are disrupting the ecological balance of New York, altering habitat and food chains. This is the state’s fourth annual Invasive Species Week, during which agencies across the state work to educate residents on the detrimental impacts of invasive species.

The aquatic plant water chestnut is the most visible invasive species in the region covered by the St. Lawrence-Eastern Ontario Partnership for Regional Invasive Species Management, which includes Oneida County, said Rob Williams, invasive species program coordinator.

“It grows to the point where it completely covers surface waters, making them unsuitable for recreation,” he said. “You can’t swim in them. You can’t canoe in them. You can’t drag a fishing lure through them.”

Asked about invasive species of most concern in Central New York, Carrie Brown-Lima, director of the New York Invasive Species Research Institute based at Cornell University, turned her eyes toward the forests.

“New York state has more invasive forest pests than any other state in the U.S. We are way up there,” she said.

The emerald ash borer, already in Oneida County and several other counties, eventually will kill every ash tree in the state, hurting industries that rely on ash wood and forcing municipalities to pay to cut down dead trees, Brown-Lima said. And the hemlock woolly adelgid threatens hemlocks, a prominent tree in the Adirondacks and one whose loss will take a big ecological toll, she said.

“There’s really no other species we have in our forest right now that can replace them,” Brown-Lima said.

A beetle that eats adelgids being raised at Cornell may be able to control woolly adelgids, but the ash borer is spreading too quickly for a predator to stop them, she said.

The PRISM concentrates it efforts on preventing new invasive species from moving into the region. Williams said he’s particularly concerned about a plant called mile-a-minute vine. “We hope it doesn’t become established in the region because it’s one of those plants that grows up to six inches a day. It literally will smother or blanket anything it grows near,” he said.

He’s also concerned about the northern snakehead, a fish that competes with native fish for habitat and food.

“It’s kind of king of the hill,” he said. “It’s so aggressive. It will wipe out other fish populations, native fish populations, in favor of itself.”